llvm-project/libcxx/include/bit

// -*- C++ -*-
//===------------------------------ bit ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//

#ifndef _LIBCPP_BIT
#define _LIBCPP_BIT

/*
    bit synopsis

namespace std {

} // namespace std

*/

#include <__config>

#if defined(__IBMCPP__)
#include "support/ibm/support.h"
#endif
#if defined(_LIBCPP_COMPILER_MSVC)
#include <intrin.h>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
unsigned __ctz(unsigned __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned>(__builtin_ctz(__x));
#else
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long where;
  // Search from LSB to MSB for first set bit.
  // Returns zero if no set bit is found.
  if (_BitScanForward(&where, __x))
    return where;
  return 32;
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
unsigned long __ctz(unsigned long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned long>(__builtin_ctzl(__x));
#else
    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
    return __ctz(static_cast<unsigned>(__x));
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
unsigned long long __ctz(unsigned long long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned long long>(__builtin_ctzll(__x));
#else
    unsigned long where;
// Search from LSB to MSB for first set bit.
// Returns zero if no set bit is found.
#if defined(_LIBCPP_HAS_BITSCAN64)
    (defined(_M_AMD64) || defined(__x86_64__))
  if (_BitScanForward64(&where, __x))
    return static_cast<int>(where);
#else
  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
  // Scan the Low Word.
  if (_BitScanForward(&where, static_cast<unsigned long>(__x)))
    return where;
  // Scan the High Word.
  if (_BitScanForward(&where, static_cast<unsigned long>(__x >> 32)))
    return where + 32; // Create a bit offset from the LSB.
#endif
  return 64;
#endif // _LIBCPP_COMPILER_MSVC
}

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
unsigned __clz(unsigned __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned>(__builtin_clz(__x));
#else
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long where;
  // Search from LSB to MSB for first set bit.
  // Returns zero if no set bit is found.
  if (_BitScanReverse(&where, __x))
    return 31 - where;
  return 32; // Undefined Behavior.
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
unsigned long __clz(unsigned long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned long>(__builtin_clzl (__x));
#else
    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
    return __clz(static_cast<unsigned>(__x));
#endif
}

inline _LIBCPP_INLINE_VISIBILITY
unsigned long long __clz(unsigned long long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
    return static_cast<unsigned long long>(__builtin_clzll(__x));
#else
  unsigned long where;
// BitScanReverse scans from MSB to LSB for first set bit.
// Returns 0 if no set bit is found.
#if defined(_LIBCPP_HAS_BITSCAN64)
  if (_BitScanReverse64(&where, __x))
    return static_cast<int>(63 - where);
#else
  // Scan the high 32 bits.
  if (_BitScanReverse(&where, static_cast<unsigned long>(__x >> 32)))
    return 63 - (where + 32); // Create a bit offset from the MSB.
  // Scan the low 32 bits.
  if (_BitScanReverse(&where, static_cast<unsigned long>(__x)))
    return 63 - where;
#endif
  return 64; // Undefined Behavior.
#endif // _LIBCPP_COMPILER_MSVC
}

inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned __x) {
#ifndef _LIBCPP_COMPILER_MSVC
  return __builtin_popcount  (__x);
#else
  static_assert(sizeof(unsigned) == 4, "");
  return __popcnt(__x);
#endif
}

inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
  return __builtin_popcountl (__x);
#else
  static_assert(sizeof(unsigned long) == 4, "");
  return __popcnt(__x);
#endif
}

inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long long __x) {
#ifndef _LIBCPP_COMPILER_MSVC
  return __builtin_popcountll(__x);
#else
  static_assert(sizeof(unsigned long long) == 8, "");
  return __popcnt64(__x);
#endif
}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_BIT